A wireless personal area network is a local area network that enables a device under a work environment of a person and devices present on the periphery thereof to be mutually interconnected.
In recent years, in such a wireless personal area network, communication devices, which are compliant with the specification of IEEE 802.15.4, that are small-sized and low-priced and are capable of performing low-output digital radio communication are used.
A network that is compliant with the specification of IEEE 802.15.4 is configured by two types of devices including an FFD (Full Function Device) and an RFD (Reduced Function Device) when the devices are broadly classified.
The FFD is a full-function built-in device having a function for approving the participation of a new device to participate in a personal area network (PAN) to which the FFD belongs and a function for defining a superframe used in communication with the other devices. Among such FFDs, a device that is present solely in each network and further has a function for determining an ID of the whole network is called a PAN coordinator.
On the other hand, the RFD is a device that does not have the participation approval function and the superframe defining function described above, which are included in the FFD, and is a function-limited-type device that has the same functions as those of the FFD except for such functions.
FIG. 8 is a schematic diagram that illustrates topologies of conventional networks configured by FFDs and RFDs. As illustrated in FIG. 8, as topologies of such a network, there are topologies of a star-type network (FIG. 8(A)), a peer-to-peer network (FIG. 8(B)), and the like.
The star-type network is configured by a PAN coordinator and a plurality of FFDs or RFDs. Among all the devices, master-slave relations are formed (see Patent Literature 1). By periodically transmitting a synchronization signal (beacon) from an FFD that is a master positioned at a higher level to the FFDs or RFDs that are slaves positioned at a lower level, synchronization between the master and each slave is established, and information is transmitted and received using a TDMA (Time Division Multiple Access) system.
On the other hand, the peer-to-peer network is similar to the star-type network described above in that the network is configured by a PAN coordinator and a plurality of FFDs or RFDs but has a difference from the star-type network in that all the devices are equal, in other words, the master-slave relation is not formed between devices. Between the devices configuring the peer-to-peer network, information is transmitted and received using a CSMA (Carrier Sense Multiple Access) system.